Flow cytometry of lesional skin enhances the evaluation of cutaneous B-cell lymphomas

Background Cutaneous B-cell lymphoproliferative lesions can pose diagnostic challenges. This study investigates the utlility of flow cytometry in 42 cases of suspected cutaneous B-cell lymphoma. Methods All available cases were reviewed [World Health Organization-European Organization for Research and Treatment of Cancer (WHO-EORTC) classification]. Flow cytometry, immunohistochemistry and polymerase chain reaction-immunoglobulin H (PCR-IgH) analysis of blood and/or lesional skin were performed on primary cutaneous B-cell lymphoma (pcBCL, 17 cases), secondary cutaneous BCL (scBCL, 8 cases) and atypical lymphoid hyperplasia (ALH, 17 cases). Results Flow cytometry of skin detected a B-cell clone in 3/13 cases of ALH, 8/8 cases of pcBCL and 4/4 cases of scBCL, while PCR detected a clone in 3/14 cases of ALH, 4/15 cases of pcBCL and 6/8 cases of scBCL. Of eight cases of pcBCL analyzed by both methods, all eight were positive by flow while only three were positive by PCR. All cases positive by PCR were also positive by flow. Of five cases with both flow and light chain immunohistochemistry, all five showed light chain restriction by flow, while only two were positive by immunohistochemistry. Conclusion Flow cytometry is more sensitive than PCR in detecting B-cell lymphoproliferative disorders (12/12 cases, 100% vs. 10/23 cases, 43%; p <0.001). Furthermore, flow cytometry complements immunohistochemistry in the detection of light chain restriction.